How did life begin on Earth?

LINDAU, Germany—What steps led to the origin of life on Earth? Scientists may be zeroing in on that most profound of questions. “We’ve gone a long way to showing” the processes that “set the stage” for cellular life on Earth, Jack Szostak said Tuesday here in his talk at the 60th annual Nobel Laureate Lectures at Lindau.

Recent findings—such as that life seems to be everywhere on Earth—have encouraged scientific inquiries into the nature of life’s beginnings, said Szostak. Along with Elizabeth H. Blackburn and Carol W. Greider, Szostak won the 2009 Nobel Prize in Physiology or Medicine for work in understanding telomeres [see Blackburn and Greider's Scientific American article “ Telomeres, Telomerase and Cancer ”]. His talk focused on his recent research on life’s start [see his Scientific American 2009 article, “The Origin of Life on Earth”]. He cited discoveries of microbes eking out existence in steaming hot springs in Yellowstone, in an acidic environment in Rio Tinto, Spain, and other hostile locations. “Even in rocks, there’s life,” he added, showing the audience an image of a green streak tenaciously spreading through rock. “Once life gets started, it can adapt and colonize many, many different environments.” In addition, astronomers have found hundreds of planets in other solar systems, and the space-based Kepler telescope recently identified more than 700 more candidate exoplanets. Many of those could have Earth-like conditions, raising the possibility that they also could harbor some form of life. How common might life be? “The question is: Is it easy or hard to make the transition in the chemistry of planets from not alive to alive?” asked Szostak.

Two critical needs for life are to create a membrane, which defines a boundary that can contain genetic material, and to replicate. Szostak said it is relatively easy to create a membrane from fatty acids that could have arisen in conditions that mimic early Earth; fatty acids, mixed in water with a little salt, readily create closed structures called vesicles.

Simple enough. But it took 10 years, said Szostak, to figure out how such material could grow and divide before the era of genetic machinery. In combination with certain molecules, scientists eventually learned, the once-stable vesicles grow long threadlike “tails.” “They become fragile in this shape,” said Szostak. “With a little disturbance, they divide.” These and other developments, such as how the primitive cells could have begun to acquire additional features that conveyed some advantage, offer a logical pathway to early evolution. “It’s something you can even imagine happening on the early Earth,” he said.

In a subsequent talk, John C. Mather, winner, with George S. Smoot, of the 2006 Nobel Prize in Physics, discussed, among other astrophysics questions, how the universe enabled conditions favorable to life. In explaining the early universe’s structure and evolution, “Astronomers have the easy part, I think,” he joked. Astronomers say, “OK, biologists, you have the next step [in describing life’s possible beginnings].” He noted that the upcoming James Webb Space Telescope, successor to the Hubble Space Telescope, will, among other things, seek Earth-like planets and glean clues about their chemistry—and whether they might harbor life.

Learn more about the Lindau meeting at Scientific American's sister publication Nature, the international journal of science, and a special web site featuring Lindau blogs, organized by Nature and Spectrum der Wissenshaft, Scientific American ’s German language edition. A slide show, Discoveries 2010: Energy, covers another Lindau initiative, a museum exhibit on energy sources.

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